Ripening dynamics of fruit quality and bioactive compounds determine optimal harvest timing in Japanese plum cultivars

Harvest timing is one of the most critical factors influencing the quality attributes of plum fruits. This study aimed to evaluate the ripening-dependent changes in fruit characteristics of five Japanese plum ( Prunus salicina L.) cultivars, namely ‘Black Amber’, ‘Black Diamond’, ‘Queen Rose’, ‘Obilnaja’, and ‘Angeleno’, at different maturity stages. Fruit samples were collected at three distinct ripening stages, and both quality parameters and biochemical traits were assessed in relation to maturity progression. Based on the overall mean of all cultivars from the initial to the final harvest stage, fruit weight (FW), total soluble solids (TSS), total phenolic content (TPC), antioxidant activity (AA), and total anthocyanin content (TAC) increased by 24.90%, 35.02%, 13.12%, 5.65%, and 4.5-fold, respectively. TSS content ranges from 14.76% (Black Amber) to 17.50% (Angeleno), titratable acidity (TA) content ranges from 0.74 (Black Diamond) to 2.35 (Obilnaja), and TP content ranges from 145.52 (Queen Rose) to 368.95 (Angeleno), TAC between 9.89 (Black Amber) and 49.21 (Black Diamond), and AA content between 106.48 (Queen Rose) and 180.71 (Angeleno). In contrast, fruit flesh firmness (FFF), peel hue angle, and TA decreased by 62.84%, 50.96%, and 49.66%, respectively. Principal component analysis (PCA) revealed that the first two principal components accounted for 68.60% of the total variation among the evaluated traits, indicating a clear differentiation of quality attributes across ripening stages. The results demonstrated that early harvesting should be avoided to ensure superior fruit quality. The findings indicate that late-harvested fruits accumulate higher concentrations of bioactive compounds, thus enhancing nutritional and functional quality; however, simultaneous fruit softening imposes limitations on post-harvest processing and marketability. These results provide a cultivar-specific, multi-dimensional framework for optimizing harvest strategies to meet diverse marketing, storage, and health-conscious consumer demands for Japanese plum cultivars.